This invention relates to the connection between the thin-walled small diameter catheter for insertion into the lumen of a human and its respective attachment hub with a larger inside diameter. The hub is made with a luer thread to connect to the supply for the administration fluid. More specifically, the disclosure relates to a unique dielectric welding attachment between the catheter and hub which attachment forms a fluid tight connection to prevent leakage or turbulence of the flow of fluid through the hub and into the smaller diameter of the catheter.
In the past, prior patents have disclosed techniques for connecting catheter tubing to hubs. One such U.S. Pat. No. 4,354,495 shows an injection molding operation used to attach the hub to the catheter. The distal end of the catheter has a thread-like configuration induced by heating and swelling the catheter at its distal end to form the helix of the thread. This thread-like member is used as a situs about which the injection molded hub can adhere. This connection is primarily mechanical. The internal juncture in bore and between the proximal end of the catheter and the distal end of the hub are not smooth and do not form a smooth transition for the flow of the administrated fluid.
U.S. Pat. No. 4,177,809 shows a three-piece configuration for mounting the catheter to the hub. The distal end of the catheter is surrounded by a funnel-shaped wedge inserted between it and the inside diameter of the hub to act as a key or keeper to retain the catheter in its axial position relative to the hub. This force fit is merely mechanical. Even though the wedge has a funnel-like interior, there is still a shoulder between it and the inside diameter of the hub and there is absolutely no teaching of welding.
U.S. Pat. No. 3,720,210 shows another way of flanging the distal end of the catheter with a curl in order to form a place at which an insert molded hub can be affixed without concern for the two separating from one another. The connection is mechanical.
U.S. Pat. No. 4,419,095 discloses RF heating to butt weld the ends of two tubes together. The outside mandrel has a convex surface in order to allow air to escape therefrom during welding. There is also a recess along the outside wall of an end of one of the tubes in order to facilitate the removal of air. The inside mandrel has an insulated sleeve over it to facilitate the weld and prevent the inside of the tube from sticking to the inside mandrel. There is absolutely no teaching of changing the overall configuration of the two tubes during the welding process. The process is merely designed to melt the tubing at the interface.
U.S. Pat. No. 3,966,520 shows ultrasonic welding as opposed to RF welding wherein a conically-shaped tool surrounds the ends of one tube that extends over in a lap joint about another tube. Ultrasonic vibrations in the frequency range of 20 to 40 kHz are used during swaging the outer tube toward the underlapping inner tube and in doing so tends to chamfer the leading end of the outer overlapping tube. The internal juncture between the tubes has the same configuration with a shoulder, there is no smooth transition between them even though an inside mandrel is used to support the overlapped tubing during the ultrasonic vibration forming operation.
U.S. Pat. No. 4,430,083 is typical of state of the art prior patents in that it shows a catheter receiving hub wherein there is an enlarged recess to receive the catheter such that the flow through the inside of the passageway through the tube is uniform. This requires that the hub be molded from both directions and a split set of core pins be used. This approach, while possible, does not afford the best possible fused junction between the hub inside diameter passage and the thin walled small catheter bore and may leave flash at the site where the core pins meet.
Therefore, it is an object of the present invention to provide a juncture between the hub and the catheter which forms a smooth, funnel-like transition from the larger inside diameter of the hub to the smaller inside bore of the catheter with no discontinuity along the wall to affect the flow of fluid therethrough.
It is a further object of the present invention and the preferred embodiment to disclose a quick, efficient means by which the distal end of the catheter and the proximal end of the hub can be joined together using dielectric welding leaving a clean internal connection therebetween without excess adhesives, flash from molding operations or additional component parts to wedge and force-fit the two together.
Consistent with the foregoing objects and in order to overcome the problems besetting the prior art, the present disclosure which follows seeks to disclose and explain a preferred embodiment in which the connection between the distal end of the catheter and the proximal end of the hub form a clean, continuous fluid tight internal junction having a smooth transition from the larger diameter of the inside of the hub to the smaller diameter of the inside of the catheter.